Molding is a process by virtue of which a molded article can be formed from molding material (such as Polyethylene Teraphalate (PET), Polypropylene (PP) and the like) by using a molding system. Various molded articles can be formed by using the molding process, such as an injection molding process. One example of a molded article that can be formed, for example, from PET material is a preform that is capable of being subsequently blown into a beverage container, such as, a bottle and the like.
As an illustration, injection molding of PET material involves heating the PET material (ex. PET pellets, etc.) to a homogeneous molten state and injecting, under pressure, the so-melted PET material into a molding cavity defined, at least in part, by a female cavity piece and a male core piece mounted respectively on a cavity plate and a core plate of the mold. The cavity plate and the core plate are urged together and are held together by clamp force, the clamp force being sufficient enough to keep the cavity and the core pieces together against the pressure of the injected PET material. The molding cavity has a shape that substantially corresponds to a final cold-state shape of the molded article to be molded. The so-injected PET material is then cooled to a temperature sufficient to enable ejection of the so-formed molded article from the mold. When cooled, the molded article shrinks inside of the molding cavity and, as such, when the cavity and core plates are urged apart, the molded article tends to remain associated with the core piece. Accordingly, by urging the core plate away from the cavity plate, the molded article can be demolded, i.e. ejected off of the core piece. Ejection structures are known to assist in removing the molded articles from the core halves. Examples of the ejection structures include stripper plates, ejector pins, etc.
One consideration for economic operation of such an injection molding system is minimizing of what is known as “cycle time”, i.e. duration of time between initiation of injection of a first molded article and initiation of injection of a second molded article, the second molded article being produced during a subsequent molding cycle. Several solutions have been proposed in the art to decrease the cycle time, some of such solutions including (i) conformal cooling for in-mold cooling, whereby cooling channels are configured to closely conform to the shape of the molded article, (ii) post-mold cooling in auxiliary post-mold cooling devices and the like.
U.S. patent application bearing publication number 2008/0026239 A1 published on Jan. 31, 2008 to Baboni et al. discloses a preform that is formed by an upper neck which maintains unchanged its form in the final object and a hollow body, joined to the neck. The method foresees the insertion, within a matrix cavity, of a metered body of polymeric material whose mass is metered according to a reference value, and the subsequent pressure insertion of a punch within the matrix cavity until it closes the mold's molding chamber, the punch conferring the shape to the inner surface of the preform and the matrix having an inner surface which confers the shape to the outer surface of the preform. According to the invention, in the molding of the preform, the error of the mass of the metered body with respect to the reference value is distributed in the hollow body, which undergoes a subsequent hot deformation until it achieves the final shape. In the mold, the matrix comprises at least one deformable wall (31) whose inner surface defines at least part of the inner surface of the matrix part intended to give form to the hollow body of the preform, said deformable wall (31) having, at least in part, a relatively thin thickness which permits it to be elastically deformed under the pressure of the polymeric material in the final preform molding step, thereby varying the thickness of the hollow body.
U.S. patent application bearing publication number 2006/0131788 A1 published on Jun. 22, 2006 to Takigawa teaches a process whereby before completion of a mold closing step of a mold apparatus, a movable member of one mold is pressed against the other mold, the movable member partially defining a cavity of the mold apparatus; charging a molding material into the cavity of the mold apparatus is started; and after completion of the mold closing step, a mold clamping step of the mold apparatus is performed so as to produce a molded product. The movable member, which partially constitutes a mold, is operated in the mold closing step so as to prevent leakage, through a clearance between parting faces, of a molding material which has begun to be charged into a cavity of the mold before completion of the mold closing step, whereby, even when the mold has a simple structure using no special component members, a molded product having a shape resembling that of a three-dimensional, deep-bottomed, concave container having a thin side wall can be produced in short time.
U.S. Pat. No. 5,439,371 issued to Sawaya on Aug. 8, 1995 teaches a locally pressurizing type injection molding machine that includes a stationary die and a movable die, so that a molded product can be formed by charging a resin into a cavity defined between the dies. A pressurizing pin extends through the movable die and has its tip end facing at least one of a resin passage and the cavity. A pressurizing cylinder is disposed at the rear of the pressurizing pin to move the pressurizing pin through the pressurizing rod. Therefore, the resin charged in the cavity can be pressurized by advancing the pressurizing pin into a resin passage, for example, a gate, the cavity or the like and hence, it is possible not only to provide an extremely thin molded product, but also to prevent the generation of a sink mark. The area occupied by the movable platen can be reduced by disposing the pressurizing rod and ejector rod coaxially.
U.S. Pat. No. 7,293,981 B2 issued to Niewels on Nov. 13, 2007 discloses a method and apparatus for compressing melt and/or compensating for melt shrinkage in an injection mold. The apparatus includes a cavity mold portion adjacent a cavity plate, a core mold portion adjacent a core plate, a mold cavity formed between the mold portions, and at least one piezoceramic actuator disposed between either or both of the core plate and the core mold portion and the cavity plate and the cavity mold portion. A controller may be connected to the at least one piezoceramic actuator to activate it, thereby causing the mold cavity volume to decrease, compressing the melt.
U.S. Pat. No. 5,662,856 issued to Wunderlich on Sep. 2, 1997 teaches a system whereby hollow plastic articles are produced by a method wherein molten material is first conveyed at low pressure via a telescoping nozzle, across compensating rods in the melt passages and individually circumferential flow passages of common primary distribution spools into transfer reservoirs. Upon completion of the controlled filling phase, primary and secondary distribution spools are shifted, the mold manifold assembly with the transfer housing together with the mold cavity bottoms and outside wall-forming sleeves are drawn in unison against stationary displacement plugs which transfer the molten material from the transfer reservoirs around the fixed-position core pin tips and into corresponding mold cavities. After completion of the cavity filling phase, the common secondary distribution spools, located close to the mold cavity bottom gates, are shifted laterally such that their land areas shut off the external melt streams. The manifold assembly, together with the now sealed cavity bottoms and outside wall-forming sleeves, move toward the fixed position core pins, whereby the molten material flowing in the same direction is condensed into the final shape of the hollow plastic article. Upon solidification, the mold is opened and the molded hollow articles are rotated or shuttled on the cooling core pins in a vertical or horizontal plane outside the molding machine clamp to subsequent cooling and ejection stations. During the hollow plastic article condensing phase, the primary distribution spools are shifted laterally again to open the passages from the plasticizer to refill simultaneously the individual transfer reservoirs with molten material.
PCT patent application bearing a publication number 2007/039766 A1 published on Apr. 12, 2007 to Clarke teaches a mould for mounting between the relatively movable platens of an injection moulding press for injection impact compression moulding of an article. The mould comprises a cavity plate (18) formed with a depression (40), a core plate (12) having a projecting core (46) at least part of the outer surface of which is cylindrical and a closure plate (14) movable relative to the core plate (12) and the cavity plate (18) and having a surface in sealing contact with the cylindrical outer surface of the core (46). A locking mechanism (70, 72) is provided to lock the closure plate (14) relative to the cavity plate (18) while permitting the core plate (12) to move relative to the cavity plate (18).